Free AI Content Detector
Paste any text and get an instant probability score of whether it was written by AI or a human. Uses a RoBERTa-based classifier model trained by OpenAI, running entirely in your browser via Transformers.js. No signup, no server, no API calls. Your text stays on your device.
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How Does AI Content Detection Work?
AI content detectors work by analyzing patterns in text that distinguish human writing from machine-generated output. This tool uses a RoBERTa-based classifier model that was fine-tuned by OpenAI specifically for detecting AI-generated text. It examines statistical properties like token probability distributions, sentence structure uniformity, and vocabulary predictability to produce a confidence score.
Unlike cloud-based detectors like GPTZero, Turnitin AI Detection, or Originality.ai that require you to upload your text to their servers, this tool runs the entire model locally in your browser via Transformers.js. Your text never leaves your device — making it safe to check sensitive academic papers, confidential documents, or private content without privacy concerns.
The model achieves approximately 95% accuracy on GPT-2 generated text. Accuracy may vary with newer AI models like GPT-4, Claude, or Gemini, as detection becomes harder as language models improve. For best results, provide at least 50 words — longer samples produce significantly more reliable predictions. No AI detector is perfect, and results should be considered one signal among many.
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How It Works
Paste or type the text you want to analyze.
Click Detect — the AI model classifies the text locally in your browser.
See the probability score of AI-generated vs human-written content.
Key Features
Privacy & Trust
Use Cases
Frequently Asked Questions
Is this AI content detector completely free?
Yes, it is 100% free with no word limits, no daily scan caps, and no signup required. Commercial AI detectors like GPTZero ($10-25/month), Originality.ai ($15-50/month), and Turnitin (institutional pricing) all charge per scan or require subscriptions. Because this tool runs the detection model locally in your browser, there are no server costs, which means unlimited free scans for as long as you need.
Is my text sent to a server when I run detection?
No. The entire RoBERTa classification model runs inside your browser via WebAssembly and Transformers.js. Your text never leaves your device — there are no API calls, no cloud uploads, and no logging of your content. This is a major advantage over cloud-based detectors where your text is sent to and stored on third-party servers. You can safely check sensitive academic papers, client content, confidential business writing, or any text you want to keep completely private.
How accurate is this AI detector and can I trust the results?
The RoBERTa-based detector was fine-tuned by OpenAI and achieves approximately 95% accuracy on GPT-2 generated text, which is what it was specifically trained for. On text from newer models like GPT-4, Claude, and Gemini, accuracy is lower because these models produce more natural-sounding output that is harder to distinguish from human writing. No AI detector — including commercial ones — achieves perfect accuracy on modern LLM output. Treat the probability score as one data point, not a definitive verdict. False positives (flagging human text as AI) and false negatives (missing AI text) both occur.
What AI detection model does this tool use?
It uses the roberta-base-openai-detector model, a RoBERTa classifier (125 million parameters) that OpenAI fine-tuned specifically for distinguishing AI-generated text from human writing. RoBERTa (Robustly Optimized BERT) is a transformer-based language model developed by Meta AI. The detector analyzes statistical patterns in your text — token probability distributions, sentence uniformity, vocabulary predictability — and outputs a probability score for "AI-generated" versus "human-written."
How much text do I need for reliable AI detection results?
For meaningful results, provide at least 50 words — ideally 150 words or more. Longer samples give the model more statistical signal to work with, producing significantly more reliable predictions. Very short texts (under 30 words) do not contain enough patterns for the classifier to analyze and will produce unreliable, essentially random scores. If you need to check a short passage, try including the surrounding paragraphs for context to improve accuracy.
Can this detect text from ChatGPT, GPT-4, Claude, or Gemini?
The model was originally trained on GPT-2 output, so it is most accurate at detecting GPT-2 style text. It can pick up some AI patterns in text from newer models (ChatGPT, GPT-4, Claude, Gemini) because there are shared statistical characteristics across AI-generated text. However, newer models produce increasingly natural output, and detection accuracy drops correspondingly. This is a limitation shared by all AI detectors — the cat-and-mouse game between generation and detection continues to evolve.
Why does the AI detection model take so long to load initially?
The RoBERTa model is approximately 350MB in size and needs to download to your browser cache on first use. On a typical broadband connection, this takes 1-3 minutes. Once cached, subsequent visits load much faster because the model is read from local storage. If the download fails or stalls, try refreshing the page, checking your internet connection, or clearing browser cache and retrying. The large model size is the tradeoff for running a real neural network locally rather than making API calls.
How does this compare to GPTZero, Turnitin AI, or Originality.ai?
The core concept is similar — all use machine learning classifiers to estimate the probability that text is AI-generated. The key differences: this tool runs entirely in your browser with complete privacy (your text never leaves your device), while GPTZero, Turnitin, and Originality.ai are cloud services that process your text on their servers. Commercial detectors may use more recent or larger models and can achieve better accuracy on modern LLM output. The tradeoff here is maximum privacy and zero cost versus potentially higher accuracy from paid cloud services.
Can this tool be fooled by paraphrasing or AI humanizer tools?
Yes, to some degree. Text that has been paraphrased, humanized, or manually edited after AI generation can reduce the AI probability score because these modifications break the statistical patterns the detector looks for. This is true of all AI detectors, not just this one. The more a human edits and personalizes AI-generated text, the harder it becomes for any detector to distinguish it from original human writing. This is why AI detection results should be treated as probability estimates, not binary verdicts.
Does this work for detecting AI-generated text in languages other than English?
The roberta-base-openai-detector model was trained primarily on English text, so it works best with English content. Applying it to other languages will produce unreliable results because the model's understanding of what "human-like" versus "AI-like" patterns look like is based on English language statistics. For non-English AI detection, you would need a detector trained on that specific language, which this tool does not currently offer.
Should I use AI detection results as definitive proof that something was written by AI?
No. AI detection scores are probabilistic estimates, not proof. Even the best commercial detectors have documented false positive rates — flagging genuine human writing as AI-generated. Academic institutions, publishers, and employers should not use any single AI detection score as the sole basis for accusations or disciplinary action. The score is one signal among many and should be combined with other evidence and human judgment.
Limitations
- Detection accuracy varies with text length and style
- Works best with English text of 50+ words
- No AI detector is 100% accurate
- Model download is ~350MB on first use
- Short texts produce less reliable results